Billionaire David Tepper's hedge fund, Appaloosa Management, reported in a letter to investors that it returned 16.8% in the first half of 2013, outperforming the S&P 500. This continues Tepper's record of strong returns for his investors, with net annualized returns of 28% over the last 20 years. A major contributor to Appaloosa's outperformance so far in 2013 has traditionally been an industry hated by investors: legacy airlines. We track quarterly 13F filings from hundreds of hedge funds, including Appaloosa, as part of our work researching investment strategies; we have found, for example, that the most popular small cap stocks among hedge funds earn an average excess return of 18 percentage points per year (learn more about our small cap strategy) and our own portfolio based on these techniques has outperformed the S&P 500 by 33 percentage points in the last 11 months.